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Science: Stars observed falling into black hole

1 February 1992

By
JEFF HECHT in
BOSTON

The Hubble Space Telescope has photographed the nucleus of a galaxy
in greater detail than ever before, and found evidence that a black hole
with a mass 2.6 billion times that of the Sun is pulling stars toward the
galaxy’s centre. According to Tod Lauer of the National Optical Astronomy
Observatories in Arizona, the density of stars in M87, a galaxy 52 million
light years away in the Virgo Cluster, reaches a peak at least 500 times
higher than expected for a normal galaxy.

In 1978, the late Peter Young of the California Institute of Technology
predicted that the gravitational pull of a massive black hole would produce
such a sharp density peak at the centre of M87. However, observations from
the ground were inconclusive. Now the much higher resolution of the Hubble
images has revealed that the star density does indeed have the peak that
Young predicted, and does not flatten out as in a normal galaxy.

This is the first evidence of a black hole distorting the centre of
a galaxy, Lauer says. However, the images do not prove beyond a doubt that
a black hole exists in M87. The best evidence, says Lauer, would be spectra
showing the motion of stars near the galactic centre. The Hubble telescope
may be up to the task when its defective optics are fixed.